Real-Time Observation of the Regime Transition Dynamics of Mode-Locked Fiber Lasers

Abstract

Mode-locked lasers exhibit complex nonlinear dynamics. Precise observation of these dynamics will aid in understanding of the underlying physics and provide new insights for laser design and applications. The starting dynamics, from initial noise fluctuations to the mode-locking regime, have previously been observed directly by time-stretched transform-based real-time spectroscopy. However, the regime transition dynamics, which are essential processes in mode-locked lasers, have not yet been resolved because regime transition process tracking is very challenging. Here we demonstrate the first insight into the regime transition dynamics enabled by our design of a real-time programmable mode-locked fibre laser, in which different operating regimes can be achieved and switched automatically. The regime transition dynamics among initial noise fluctuations, Q-switching, fundamental mode-locking and harmonic mode-locking regimes have been observed and thoroughly analysed by both temporal and spectral means. These findings will enrich our understanding of the complex dynamics inside mode-locked lasers.

A Unified Framework for Photonic Time‐Stretch Systems

“…Now we have two nested integrals in the expression of the output electric field, E 4 (t) as shown in Equation (38). Here T = t − 𝛽 1,1 L 1 − 𝛽 1,2 L 2 is the total retarded-time variable.…”

“…[ 1,4–15 ] In the ensuing two decades, it has emerged as the most successful approach to real‐time measurements and has mutated into many variants for diverse applications including spectroscopy, imaging, vibrometry, velocimetry, radar, and lidar. [ 3 ] Time stretch has enabled the discovery of single‐shot ultrafast “rare events” such as optical rogue waves, [ 16–23 ] the birth of laser mode‐locking and internal dynamics of soliton molecules, [ 24–43 ] relativistic electron dynamics in an electron accelerator, [ 44–47 ] and dynamic chemistry during combustion. [ 48 ] Time stretch has been employed in ultrafast spectroscopy for exploring dynamical processes and nonrepetitive phenomena.…”

“…[1,[4][5][6][7][8][9][10][11][12][13][14][15] In the ensuing two decades, it has emerged as the most successful approach to real-time measurements and has mutated into many variants for diverse applications including spectroscopy, imaging, vibrometry, velocimetry, radar, and lidar. [3] Time stretch has enabled the discovery of single-shot ultrafast "rare events" such as optical rogue waves, [16][17][18][19][20][21][22][23] the birth of laser modelocking and internal dynamics of soliton molecules, [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] relativistic electron dynamics in an electron accelerator, [44][45][46][47] and dynamic chemistry during combustion. [48] Time stretch...…”

Manipulating the longitudinal mode distribution in the self-mode-locked Nd:YVO4 laser with flexible reflectivity and tilted mirror

“…[6][7][8] Among them, the SML technique is a promising method with the advantages of compactness and low cavity losses. According to previous research, since the pulse time characteristics in SML lasers mainly depend on the longitudinal mode oscillation states, [9][10][11] lots of approaches have been employed to investigate the longitudinal mode oscillation states of the SML lasers, such as controlling the laser gain, adjusting the resonant cavity length, and introducing a wavelength selector. Schfer et al controlled the longitudinal mode distribution in an Nd∶YVO 4 laser by tuning the length of the gain medium.…”

Intelligent control of mode-locked femtosecond pulses by time-stretch-assisted real-time spectral analysis

“…Combined with a real-time oscilloscope, a TS-DFT operates as a real-time OSA, resolving the issue of the low frame rate in a traditional OSA 20 . In numerous works, TS-DFT-based fast spectral analysis has been used with mode-locked lasers to observe soliton dynamics, including soliton explosions 21,22 , build-up processes of various pulsation regimes [23][24][25] , dissipative solitons 26 , soliton molecules [27][28][29] , sophisticated soliton dynamics [30][31][32][33][34] , and the transition dynamics between pulsation regimes 35,36 . In this article, for the first time, we propose using TS-DFT-based fast spectral analysis as the discrimination criterion to achieve rich modelocking regimes.…”